1. Field of the Invention
The present invention relates to a method for forming a silicon oxide film, a plasma processing apparatus and a storage medium, and in particular relates to the method for forming the silicon oxide film, plasma processing apparatus and storage medium, each applicable to the case of forming the silicon oxide film used as an insulating film in a process for manufacturing, for example, various semiconductor devices or the like.
2. Background Art
In the process for manufacturing the various semiconductor devices, the silicon oxide film, such as SiO2 or the like, which is used as the insulating film, such as a gate insulating film of, for example, a transistor, is formed. The method for forming such a silicon oxide film can be broadly divided into a thermal oxidation process employing an oxidation furnace and/or RTP (Rapid Thermal Process) apparatus and a plasma oxidation process employing a plasma processing apparatus. For instance, in a wet oxidation process using the oxidation furnace, which is one aspect of the heating process, a silicon substrate or substrates are first heated up to a temperature above 800° C., and then exposed to an oxidizing atmosphere in a WVG (Water Vapor Generator) apparatus adapted for generating steam (H2O) by combusting hydrogen with oxygen. In this manner, the surface of each silicon substrate can be oxidized, thereby forming the silicon oxide film thereon.
Meanwhile, in the plasma oxidation process, a processing gas containing an argon gas and an oxygen gas is used, with an approximately 1% flow rate of oxygen. Specifically, this plasma oxidation process is performed by applying plasma, which has been generated in a chamber under pressure of 133.3 Pa while being excited by a microwave, to each silicon surface. As used herein, such plasma excited by the microwave will be referred to as “microwave excitation plasma.” This process can facilitate control of film thickness and form the silicon oxide film having relatively high quality (see, e.g., Patent Document 1).    Patent Document 1: WO2004/008519
Recently, the thermal oxidation process has been considered as a method that can form the silicon oxide film with higher quality. However, this process should be performed at a considerably high temperature exceeding 800° C., thus being likely to increase thermal budget and have negative impact, such as deformation or warp, on each silicon substrate, due to thermal stress.
Meanwhile, the plasma oxidation process described in the above Patent Document 1 is performed at a relatively low temperature of approximately 400° C., thereby substantially avoiding such undesired increase of the thermal budget and warp of each substrate that may be caused by the above thermal oxidation process. In addition, due to the plasma process performed under the condition of approximately 1% flow rate of O2 and 133.3 Pa processing pressure (for convenience, such a condition will be, hereinafter, referred to as a “lower-pressure and lower-oxygen-concentration condition”), a significantly high oxidation rate can be achieved.
However, in the silicon oxide film obtained by such a plasma oxidation process, the insulating properties may be considerably changed, depending on the conditions of the plasma oxidation process. Therefore, in the case of manufacturing devices, such as MOS capacitors and the like, each using the silicon oxide film formed by the plasma oxidation process, as the insulating film thereof, failure of initial pressure resistance may tend to occur, thus significantly lowering the yield.